An emerging category of electronic devices is time-of-flight (TOF) systems. The TOF systems find applications in accelerometers, monolithic gyroscopes, light sensors, conveyor belts, depth sensing, proximity sensing, gesture recognition and imagers. A TOF system includes a light source that emits light pulses. The light pulses are emitted towards a target, which reflects the light pulses. The target is any object of interest which may include, but not limited to, a human, an automated component, an animal, an electronic device etc. A TOF sensor in the TOF system receives the reflected light pulses. The TOF sensor receives the reflected light pulses after a time of flight, which is proportional to a distance of the target from the TOF system.
The TOF sensor includes one or more TOF sensor pixels. Each TOF sensor pixel includes a receiver. The receiver processes the reflected light pulses to estimate the distance of the target from the TOF system. In addition to the reflected light pulses, the receiver also receives other signals such as, but not limited to, electrical interferences, crosstalk signals and ambient light. The ambient light is due to one or more of the following, but not limited to, florescent lamps, sunlight, bulbs etc.
The ambient light causes a direct current (DC) signal being generated in the receiver. A high DC signal saturates the receiver. This causes an error in estimating the distance of the target from the TOF system. In one example, a signal strength of the reflected light pulse is 30 dB whereas an interference generated is of the order of 100 dB. Thus, a receiver with high dynamic range is required.